The present invention relates to an optical filamentary material having a thermoplastic protective jacket and, more particularly, an optical filamentary material containing a core made from an optically transparent thermoplastic polymeric material.
Optical filamentary materials are well known in the art for transmission of light along a filament length by multiple internal reflections of light. Great care is taken to minimize light losses along the length of the filament or, in other words, internal reflections are made as total as possible so that light applied to one end of the optical filamentary material is efficiently transmitted to the opposite end of the material. The light transmitting portion or core of the optical filamentary material is contained with a sheath having a lower index of refraction which minimizes the escape or absorption of light along the length of the filament. This sheath is normally transparent since an opaque sheath tends to absorb light. Also, the sheath is conventionally made from a substantially amorphous material to minimize light scattering and absorption.
Optical filamentary materials can be divided into two general classes dependent upon the type of optically transparent core material. A first class of core material is thermoplastic in nature while a second class is made from glass. The first class is generally superior both in toughness and in ease of making connections while the second class is generally superior in light transmission.